Improved ion implantation method and ion implantation apparatus performing the same

ABSTRACT

The present invention provides an improved ion implantation method and an ion implantation apparatus for performing the improved ion implantation method, belongs to the field of ion implantation technology, which can solve the problem of the poor stability and uniformity of the ion beam of the existing ion implantation apparatus. The improved ion implantation method of the invention comprises steps of: step S 1 , detecting beam flow densities and beam flow distribution nonuniformities under various decelerating voltages; step S 2 , determining an operation decelerating voltage based on the beam flow densities and the beam flow distribution nonuniformities; and step S 3 , performing an ion implantation under the determined operation decelerating voltage. The present invention ensures the uniformity and stability of the ion beam, and thus ensures the uniformity of performances of the processed base materials in each batch or among various batches.

FIELD OF THE INVENTION

The invention belongs to the field of ion implantation technology, andparticularly, to an improved ion implantation method and an ionimplantation apparatus performing the same.

BACKGROUND OF THE INVENTION

Among the semiconductor device manufacturing processes, an ionimplantation process is used to perform doping on a display panel, asemiconductor wafer or other work pieces. Doping is often performed on asubstrate, and various expected effects on the substrate may be achievedby implanting a certain type of ions therein to change the diffusioncapability of a dielectric layer of the substrate.

In a practical application, an ion implantation process is performed inbatches, that is, a plurality of substrates are implanted simultaneouslyor implanted in batches. When a plurality of substrates or a pluralityof batches of substrates are processed in this manner, the ionimplantation apparatus is required to continuously generate uniform andstable ion beam.

However, when a large batches of substrates are processed by using aconventional ion implantation apparatus, the stability and uniformity ofthe ion beam are always changed, that is, when different batches ofsubstrates are processed, there are remarkable difference in thestability and uniformity of the ion beam, thus performance uniformity ofthe processed base materials in each batch or among various batchescannot be ensured. The stability and uniformity of ion implantation havebecome a problem to be solved urgently in the current semiconductorprocess. In the prior art, in order to solve the problem in stability ofion implantation, a common method used is to improve the structure ofthe apparatus, however, this method causes a high cost, and thestability of ion implantation is still low.

SUMMARY OF THE INVENTION

An object of the invention is to solve the problem of the poor stabilityand uniformity of ion implantation in the prior art, and the presentinvention provides an improved ion implantation method and an ionimplantation apparatus performing the same.

A solution adopted in the invention to solve the problem is an improvedion implantation method comprising steps of:

step 1, detecting beam flow densities and beam flow distributionnonuniformities under various decelerating voltages;

step 2, determining an operation decelerating voltage based on the beamflow densities and the beam flow distribution nonuniformities; and

step 3, performing an ion implantation under the determined operationdecelerating voltage.

Preferably, the step 1 comprises steps of:

step S11, setting initial values of parameters, including: setting aninitial value of the decelerating voltage to V₀, the beam flow densityto ρ₀, the beam flow distribution nonuniformity to x₀, an optimizationrange of the decelerating voltage to V₀±L, a control error range of thebeam flow density to p, and the beam flow distribution nonuniformity tobe less than q;

step 12, preliminarily determining starting points for optimization ofthe decelerating voltage,

wherein taking m different decelerating voltage test points within theoptimization range of the decelerating voltage V₀±L, and measuring beamflow densities ρ_(g) and beam flow distribution nonuniformities x_(g)under the m test points, respectively.

Preferably, the step S2 comprises steps of:

step S21, filtering the starting points for optimization of thedecelerating voltage, including:

taking decelerating voltages at n test points, under which the beam flowdensity ρ_(g) and the beam flow distribution nonuniformity x_(g) satisfy|ρ_(g)−ρ₀|<p and x_(g)<q, as a starting-point set for optimization ofthe decelerating voltage;

ranking the n starting points for optimization of the deceleratingvoltage according to an order of the beam flow distributionnonuniformity x_(g) from the smallest one to the biggest one, and takingthem as starting points for optimization of the decelerating voltagesequentially;

step S22, evaluating pre-operation decelerating voltages, including:

sequentially evaluating the starting points for optimization of thedecelerating voltage, performing an ion implantation process under adecelerating voltage V_(i) corresponding to the i-th starting point foroptimization of the decelerating voltage, obtaining a beam flowdistribution nonuniformity x_(i) corresponding to the deceleratingvoltage V_(i), detecting and recording corresponding beam flowdistribution nonuniformities every a predetermined time interval for ktimes, and defining the recorded beam flow distribution nonuniformitiesas X_(ir)∈[x_(i1), x_(i2), . . . , x_(ik)];

step S23, determining an operation decelerating voltage, including:

comparing an error ratio value |x_(ir)−x_(i)|/x_(i) between x_(ir) andx_(i) with a control error upper limit W of the beam flow distributionnonuniformity;

when all x_(ir) satisfy (|x_(ir)−x_(i)|/x_(i))<W, determining thedecelerating voltage V_(i) corresponding to the i-th test point as theoperation decelerating voltage; and

when at least one x_(ir) satisfies (|x_(ir)−x_(i)|/x_(i))≧W, performingthe step S22 for the decelerating voltage V_(i+1).

Preferably, p is 5%, and q is 10%.

Preferably, m is a natural number equal to or more than 10.

Preferably, L=V₀/5.

Preferably, the m test points are uniformly distributed within theoptimization range of the decelerating voltage V₀±L.

Preferably, W is 3%.

Preferably, k is a natural number equal to or more than 10.

Preferably, the step S3 comprises performing the ion implantationprocess on at least one base material under the determined deceleratingvoltage.

Furthermore, the invention further provides an ion implantationapparatus for performing the above improved ion implantation method.

In the improved ion implantation method and the ion implantationapparatus performing the improved ion implantation method in theinvention, through adjusting the decelerating voltage of thedecelerating electrode of the ion implantation apparatus, an operationdecelerating voltage of the decelerating electrode is determined so thatthe beam flow density and the beam flow distribution nonuniformity arewithin a predetermined control range, thus the uniformity ofperformances of the base materials in the same batch and among batchesis ensured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of an ion beam control method of an ionimplantation apparatus in the embodiment 1 of the present invention.

FIG. 2 is a flowchart illustrating how to detect the beam flow densitiesand the beam flow distribution nonuniformities under variousdecelerating voltages in the embodiment 1 of the present invention.

FIG. 3 is a flowchart illustrating how to determine the operationdecelerating voltage based on the beam flow densities and the beam flowdistribution nonuniformities in the embodiment 1 of the presentinvention.

DETAILED DESCRIPTION OF EMBODIMENTS

In order to make persons skilled in the art better understand thesolutions of the present invention, the present invention will befurther described in detail below in conjunction with the drawings andembodiments.

The present invention provides an improved ion implantation method,which may be used in any type of ion implantation, so that the beam flowdensity and the beam flow distribution nonuniformity are within apredetermined control range, so as to ensure the uniformity ofperformances of the substrates subjected to the ion implantation in thesame batch or among various batches.

Embodiment 1

As shown in FIG. 1, the invention provides an improved ion implantationmethod comprising steps of:

step S1, detecting beam flow densities and beam flow distributionnonuniformities under various decelerating voltages;

step S2, determining an operation decelerating voltage based on the beamflow densities and the beam flow distribution nonuniformities; and

step S3, performing an ion implantation under the determined operationdecelerating voltage.

Specifically, as shown in FIG. 2, the step S1 comprises following steps.

Step S11, setting initial values of parameters.

Specifically, the control parameters of an ion implantation process areset as follows: setting an initial value of the decelerating voltage toV₀, the beam flow density to ρ₀, the beam flow distributionnonuniformity to x₀, an optimization range of the decelerating voltageto V₀±L, a control error range of the beam flow density to p, and thebeam flow distribution nonuniformity to be less than q.

Preferably, the initial value of the decelerating voltage V₀ is adecelerating voltage when the former process is stable; the beam flowdensity ρ₀ and the beam flow distribution nonuniformity x₀ are the beamflow density and the beam flow distribution nonuniformity correspondingto the decelerating voltage when the former process is stable. When anoperator thinks that the ion implantation process is unstable, he/hermay adjust the decelerating voltage near its initial value V₀ to ensurethe stability of the ion implantation process among batches.

Process control parameters q, p and L of the ion implantation apparatusare set experientially depending on the performance of the ionimplantation apparatus and requirements on processing of the basematerial. Preferably, the beam flow distribution nonuniformity is lessthan 10%, namely, q is 10%; the control error range of the beam flowdensity p is 5%. Preferably, the optimization range of the deceleratingvoltage V₀±L is V₀±V₀/5.

Step S12, preliminarily determining starting points for optimization ofthe decelerating voltage,

wherein taking m different decelerating voltage test points within theoptimization range of the decelerating voltage V₀±L, and measuring beamflow densities ρ_(g) and beam flow distribution nonuniformities x_(g)under the m test points, respectively.

Preferably, m is a natural number equal to or more than 10, and the morethe test points are selected, the more accurate the decelerating voltageobtained by optimization is.

Preferably, the m test points are uniformly distributed within theoptimization range of the decelerating voltage V₀±L, so that thepreferable operation decelerating voltage is not easily be omitted.

It should be understood that, a method for detecting the beam flowdensity and the beam flow distribution nonuniformity under a specificdecelerating voltage is described above, however, other similar methodsin the prior art are applicable.

As shown in FIG. 3, the step S2 comprises following steps.

Step S21, filtering the starting points for optimization of thedecelerating voltage.

Decelerating voltages at n test points, under which the beam flowdensity ρ_(g) and the beam flow distribution nonuniformity x_(g) satisfy↑ρ_(g)−ρ₀|<p and x_(g)<q, are taken as a starting-point set foroptimization of the decelerating voltage; that is, the above m testpoints are filtered to find out n test points as the starting point setfor optimization of the decelerating voltage.

Next, the filtered n starting points for optimization of thedecelerating voltage are ranked according to an order of the beam flowdistribution nonuniformities x_(g) from the smallest one to the biggestone, used as starting points for optimization of the deceleratingvoltage sequentially, and respectively recorded as (x_(g1), x_(g2), . .. , x_(gi), . . . , x_(gn)). For a test point, the smaller the beam flowdistribution nonuniformity is, the better the quality of the ion beamthereof is, therefore, in a case that the beam flow density is within acertain error range of a set target beam flow density, a deceleratingvoltage corresponding to the test point with small beam flowdistribution nonuniformity is first selected to evaluate, wherein 1≦i≦n.

Step S22, evaluating pre-operation decelerating voltages.

The starting points for optimization of the decelerating voltage aretaken as pre-operation decelerating voltages, and the size of afluctuation range of the beam flow distribution nonuniformitiescorresponding to each pre-operation decelerating voltage at differenttime points is taken as a criterion for evaluating the pre-operationdecelerating voltage to determine whether the pre-operation deceleratingvoltage is an operation decelerating voltage.

Specifically, the pre-operation decelerating voltages are sequentiallyevaluated according to the order of the starting points for optimizationof the decelerating voltage. First, the pre-operation deceleratingvoltage V₁ determined in the step S21 corresponding to the smallest beamflow distribution nonuniformity x_(g1) is evaluated. For example, theevaluating procedure of every pre-operation decelerating voltage V_(i)is as follows: performing an ion implantation process under thedecelerating voltage V_(i) corresponding to the i-th starting point foroptimization of the decelerating voltage, obtaining a beam flowdistribution nonuniformity x_(i) corresponding to the deceleratingvoltage V_(i) in the step S12, detecting and recording correspondingbeam flow distribution nonuniformities every a time period of Δt for ktimes, and defining the recorded beam flow distribution nonuniformitiesas x_(ir)∈[x_(i1), x_(i2), . . . x_(ik)];

Preferably, k is a natural number equal to or more than 10, and the morethe test points are, the more adequate the data for optimization of thedecelerating voltage is.

It should be understood that, the above parameters may be adjusteddepending on experience and application scene, for example, the lengthof the time period of Δt and the number k of the time periods may becombinedly adjusted.

Step S23, determining an operation decelerating voltage.

comparing an error ratio value |x_(ir)−x_(i)|/x_(i) between the x_(ir)and x_(i) with a control error upper limit W of the beam flowdistribution nonuniformity;

wherein, preferably, W is 3%, which requires that the fluctuation rangeof corresponding beam flow distribution nonuniformities of thepre-operation decelerating voltage at various time points is small, andof course, W may be adjusted according to a specific application scene.

Specifically, when all x_(ir) satisfy (|x_(ir)−x_(i)|/x_(i))<W, thedecelerating voltage V_(i) corresponding to the i-th test point isdetermined as the operation decelerating voltage, the step S23 ofdetermining the operation decelerating voltage is completed, and thenthe step S3 is performed, that is, the ion implantation process isperformed under the operation decelerating voltage.

When at least one x_(ir) satisfies (|x_(ir)−x_(i)|/x_(i))≧W, i=i+1 isperformed, and the step S22 is performed, namely, the next start pointfor optimization of the decelerating voltage V_(i+1) (that is, nextper-operation decelerating voltage V_(i+1)) is evaluated, and whetherthe per-operation decelerating voltage is the operation deceleratingvoltage is determined by the step S23, if yes, the step S23 ofdetermining the operation decelerating voltage is completed and then thestep S3 is performed, namely, the ion implantation process is performedunder the operation decelerating voltage V_(i+1); and if no, the stepS22 is performed, that is, the pre-operation decelerating voltageV_(i+2) is evaluated, and whether the per-operation decelerating voltageis the operation decelerating voltage is determined by the step S23 todetermine the operation decelerating voltage. In the present embodiment,the above operations are performed repeatedly till an operationdecelerating voltage is determined.

In summary, the operation decelerating voltage obtained in embodimentsof the invention is acquired by sequentially evaluating thepre-operation decelerating voltages with respect to the selectedstarting points for optimization of the decelerating voltage in theorder of the beam flow distribution nonuniformities from the smallestone to the biggest one, that is to say, if the pre-operationdecelerating voltage V₁ corresponding to the smallest beam flowdistribution nonuniformity x_(g1) in the step S21 is determined as theoperation decelerating voltage by the step S22 and the step S23, thenthe step S3 may be performed, namely, the ion implantation process isperformed under the operation decelerating voltage V₁. If thepre-operation decelerating voltage V₁ corresponding to the smallest beamflow distribution nonuniformity x_(g1) in the step S21 is not determinedas the operation decelerating voltage by the step S22 and the step S23,then the pre-operation decelerating voltage V₂ corresponding to thesecond smallest beam flow distribution nonuniformity x_(g2) isevaluated, and so on, till an operation decelerating voltage isdetermined.

After the operation decelerating voltage is determined by the steps S21,S22 and S23 in FIG. 3, the ion implantation process is performed on atleast one base material under the determined operation deceleratingvoltage, preferably, the number of the base materials is 10, and ofcourse, the number of the base materials may be increased or reduced asdesired.

The ion implantation apparatus performs ion implantation process on thebase material under the operation decelerating voltage determinedaccording to the embodiment of the invention, the uniformity andstability of the ion beam is ensured, and thus uniformity ofperformances of the processed base materials in each batch or amongvarious batches may be ensured, therefore, uniformity of performances ofsemiconductor devices made of the base materials may be ensured.

It should be understood that, the above embodiments are only exemplaryembodiments employed to illustrate the principle of the invention, andthe invention is not limited thereto. Persons skilled in the art canmake various modifications and improvements without departing from theprinciple and substance of the invention, and these modifications andimprovements should be considered to be within the protection scope ofthe invention.

1. An improved ion implantation method comprising steps of: step S1,detecting beam flow densities and beam flow distribution nonuniformitiesunder various decelerating voltages; step S2, determining an operationdecelerating voltage based on the beam flow densities and the beam flowdistribution nonuniformities; and step S3, performing an ionimplantation under the determined operation decelerating voltage.
 2. Theimproved ion implantation method of claim 1, wherein the step S1comprises steps of: step S11, setting initial values of parameters,including: setting an initial value of the decelerating voltage to V₀,the beam flow density to ρ₀, the beam flow distribution nonuniformity tox₀, an optimization range of the decelerating voltage to V₀±L, a controlerror range of the beam flow density to p, and the beam flowdistribution nonuniformity to be less than q; and step S12,preliminarily determining starting points for optimization of thedecelerating voltage, wherein m different decelerating voltage testpoints are taken within the optimization range of the deceleratingvoltage V₀±L, and beam flow densities ρ_(g) and beam flow distributionnonuniformities x_(g) under the m test points are measured,respectively.
 3. The improved ion implantation method of claim 2,wherein the step S2 comprises steps of: step S21, filtering the startingpoints for optimization of the decelerating voltage, including: takingdecelerating voltages at n test points, under which the beam flowdensity ρ_(g) and the beam flow distribution nonuniformity x_(g) satisfy|ρ_(g)−ρ₀|<p and x_(g)<q, as a starting-point set for optimization ofthe decelerating voltage; and ranking the n starting points foroptimization of the decelerating voltage according to an order of thebeam flow distribution nonuniformities x_(g) from the smallest one tothe biggest one, and taking them as starting points for optimization ofthe decelerating voltage sequentially; step S22, evaluatingpre-operation decelerating voltages, sequentially evaluating thestarting points for optimization of the decelerating voltage, performingan ion implantation process under a decelerating voltage V_(i)corresponding to the i-th starting point for optimization of thedecelerating voltage, obtaining a beam flow distribution nonuniformityx_(i) corresponding to the decelerating voltage V_(i), detecting andrecording corresponding beam flow distribution nonuniformities every apredetermined time interval for k times, and defining the recorded beamflow distribution nonuniformities as x_(ir)∈[x_(i1), x_(i2), . . .x_(ik)]; step S23, determining an operation decelerating voltage,including: comparing an error ratio value |x_(ir)−x_(i)|/x_(i) betweenx_(ir) and x_(i) with a control error upper limit W of the beam flowdistribution nonuniformity; when all x_(ir) satisfy(|x_(ir)−x_(i)|/x_(i))<W, determining the decelerating voltage V_(i)corresponding to the i-th test point as the operation deceleratingvoltage; and when at least one x_(ir) satisfies(|x_(ir)−x_(i)|/x_(i))≧W, performing the step S22 for the deceleratingvoltage V_(i+1).
 4. The improved ion implantation method of claim 2,wherein p is 5%, and q is 10%. 5-11. (canceled)
 12. The improved ionimplantation method of claim 3, wherein p is 5%, and q is 10%.
 13. Theimproved ion implantation method of claim 2, wherein m is a naturalnumber equal to or more than
 10. 14. The improved ion implantationmethod of claim 3, wherein m is a natural number equal to or more than10.
 15. The improved ion implantation method of claim 4, wherein m is anatural number equal to or more than
 10. 16. The improved ionimplantation method of claim 12, wherein m is a natural number equal toor more than
 10. 17. The improved ion implantation method of claim 2,wherein L=V₀/5.
 18. The improved ion implantation method of claim 3,wherein L=V₀/5.
 19. The improved ion implantation method of claim 4,wherein L=V₀/5.
 20. The improved ion implantation method of claim 12,wherein L=V₀/5.
 21. The improved ion implantation method of claim 2,wherein the m test points are uniformly distributed within theoptimization range of the decelerating voltage V₀±L.
 22. The improvedion implantation method of claim 3, wherein the m test points areuniformly distributed within the optimization range of the deceleratingvoltage V₀±L.
 23. The improved ion implantation method of claim 4,wherein the m test points are uniformly distributed within theoptimization range of the decelerating voltage V₀±L.
 24. The improvedion implantation method of claim 3, wherein W is 3%.
 25. The improvedion implantation method of claim 3, wherein k is a natural number equalto or more than
 10. 26. The improved ion implantation method of claim 1,wherein the step S3 comprises a step of performing the ion implantationprocess on at least one base material under the determined operationdecelerating voltage.
 27. An ion implantation apparatus for performingthe improved ion implantation method of claim 1.